How to Complete a Bean Stitch in the Back Loops Only (bsblo)
[Yarn over, insert your hk into the indicated stitch (blo), yarn over and pull up to working height] 2 times.
Yarn over and pull through all 5 loops on the hook.
Based on your pattern instructions, you may need to repeat the steps in brackets multiple times (typically 2-4 times) depending on how "puffy" the stitch needs to be for the design.